Smoke detector



April 4, 1961 A. SCHOEPE ET AL SMOKE DETECTOR 2 Sheets-Sheet 1 FiledAug. 16, 1957 E v s T R Y mm m z. a G N O E P F W 0 LM 1 2 mm" M AAApril 4, 1961 A. SCHOEPE ET AL SMOKE DETECTOR 2 Sheets-Sheet 2 FiledAug. 16, 1957 ADOLF SCHOEPE ADAM OGI NT INVENTORS BY I'm M QJ 1:

ArTaPA/H Unite States Patent SMOKE DETECTOR Filed Aug. 16, 1957, Ser.No. 678,627

7 Claims. (Cl. 250-435) This invention relates to a smoke detector and,more particularly, to a smoke detector adapted to be utilized in varioustypes of buildings in detecting smoke prior to the commencement of afull-scale confiagration.

There are, at present, on the market various types of devices which aresensitive to the increase in temperature incidental to a full-scaleconflagration in the vicinity and there are also devices which willfunction when a relatively large amount of smoke is present. The latterdevices for detecting smoke are generally photo-electric in characterand require a relatively large quantity of dense smoke to cause theenergization of the same.

It is, therefore, an object of our invention to provide a smoke detectorwhich is extremely sensitive and which is capable of response torelatively small quantities of smoke, thus permitting the energizationof the smoke detector and the detection of smoldering fires prior to theinitiation of a full-scale conflagration.

A further object of our invention is the provision of a smoke detectorwhich includes first and second detecting means, one of which is moresensitive to ultraviolet radiation than its associated detecting means,said smoke detecting means being juxtaposed to a source of ultravioletray radiation and being incorporated inan electrical circuit having asignal emitting means therein whereby when the smoke detecting means aresubjected to the passage of smoke through the field thereof, the circuitand the signal constituting a part thereof are energized to give awarning of smoke conditions in the vicinity of the smoke detector of ourinvention.

A further object of our invention is the provision of a smoke detectingdevice of the aforementioned character wherein the more sensitive of thesmoke detecting means is constituted by a metal such as selenium,cesiumoxide, tantalum, zinc, or the like which, when exposed toultraviolet radiation becomes electronegative and which normally retainssaid electronegative charge as long as its exposure to a source ofultraviolet radiation with which it is associated 'in the smoke detectorof our invention is not interfered with.

However, we have discovered that when a smoke detecting means of theelectronegative character described immediately hereinabove isassociated with a nonsensitive detecting means or one of lesssensitivity, the exposure of the more sensitive detecting means to smokeparticles will lessen the electronegative character of the sensitiveelectronegative detecting means and cause the energization of a circuitassociated therewith to create a signal or to actuate a warning deviceassociated with the smoke detector of our invention.

Other objects and advantages of our invention will be apparent from thefollowing specification and the accompanying drawings which are for thepurpose of illustration only and in which:

Fig. 1 is a partially sectional view of a smoke detector fabricated inaccordance with the teachings of our invention;

Patented Apr. 4, 1961 Fig. 2 is a transverse, sectional view taken onthe broken line 22 of Fig. 1;

Fig. 3 is a vertical, sectional view taken on the broken line 3-3 ofFig. 2;

Fig. .4 is a schematic electrical circuit showing the various componentsthereof incorporated in the smoke detector of our invention; and

Fig. 5 is an enlarged schematic view showing the electrical relationshipbetween the first and second detectors of our invention.

Referring to the drawings and particularly to Figs. l-3 thereof, we showa smoke detector 10 constructed in accordance with the teachings of ourinvention and including a housing 12 which includes oppositely disposed,spaced end plates 14 of substantially cylindrical coufiguration.

The end plates 14, as best shown in Fig. 3 of the drawings, includeaxially extending cylindrical mounting flanges 16 formed from insulatingmaterial and provided with a plurality of mounting slots 18, for apurpose which will be described in greater detail below. The end plates14 are retained in operative and spaced relationship with each other bytie bolts 20 having nuts 22 secured to the outer extremities thereof, asbest shown in Fig. 3 of the drawings. Electrical receptors or sockets 24are mounted centrally of the end plates 14 and are adapted to receiveargon glow lamps 26 which are connected by leads 28 to a suitable sourceof electrical energy.

Mounted between the end plates 14 and supported in the slots 18 providedin the cylindrical flanges 16 thereof are individual smoke detectorsconstituted, respectively, by internested, substantially V-shaped plates30 and 32 and individual rectangular plates 34 mounted between opposedlegs of the V.-shaped plates 30. The oppositely disposed legs of theV-shaped plates 30 provide first detector elements 36 while the seconddetector elements 38 are constituted by the rectangular plates 34. Theoppositely disposed legsof the V-shaped' plates 32 constitute thirddetector elements 40.

In the present embodiment of our invention the first detector plates areformed from zinc, selenium, cesium oxide, tantalum, or other metal ormetal oxide which, When exposed to'ultraviolet radiation, acquires anelectronegative charge. Since the flanges 16 on the end plates 14 areformed from insulating material, the first detector elements constitutedby oppositely disposed legs of the V-shaped plates 30 are insulated toisolate said first detector elements 36 from ground.

The rectangular plates 34 constituting the second detector elements arepreferably formed from a material which is completely insensitive toultraviolet radiation or which is less sensitive to such ultravioletradiation than the first detector elements 36 so that when the first andsecond detector elements 36 and 38 are associated in an electroniccircuit, to be described hereinbelow, an ionization effect can becreated by the passage of smoke into the field thereof to cause theenergization of said circuit and the operation of an alarm signal orother device.

The second detector element 38 constituted by the rectangular plate 34can be fabricated from copper, carbon, or similar materials which arequite insensitive to the operation of the ultraviolet ray radiationemanating from the argon lamps 26 and which are electropositive incontradistinction to the electronegative first detector elements 36constituted by the oppositely disposedlegs of the V-shaped plates 30.

The V-shaped plates 32 are also formed from the same material as theV-shaped plates 30 and thus, when the plates 30 are formed from copper,the plates 32 will be formed from the same material.

While we have disclosed the various mechanical and electro-mechanicalelements of the smoke detector of our invention as formed inpredetermined shapes and arranged in predetermined operative andmechanical com binations, as illustrated in Figs. 1-3 of the drawings,it is, of course, conceivable that variations in the operativerelationship between the component parts such as the argon lamps 26 andthe first, second, and third detector elements may be made. However, bythe provision of a mechanical construction of the character previouslydisclosed, the infiltration of smoke between the first, second, andthird detector elements 36, 38, and 40, respectively, is facilitated sothat the operation of the smoke detector 10 of our invention is bothextremely precise and sensitive.

There is shown in Fig. 4 of the drawings an electrical circuit 50, theinput leads 52 and 54 of which are connected to a simple source of 60cycle, 115 volt, alternating current. A lead 56 is connected between theinput lead 54 and a rectifier 58 whose output of pulsating D.C. voltageis applied to the anode 60 of a thyratron tube 62. Connected across theanode 60 of the thyratron tube 62 i a capacitor 64 which is connected tothe output of the rectifier 58. A limiting capacitor 66 is disposed inparallel relationship with the capacitor 64.

The first detector element 36 is connected through a resistance 70 tothe grid 72 of the thyratron tube 62 and is exposed to the ultravioletray radiation from the argon gas glow lamp 26. Incidentally, the glowlamp 26 utilized is an AR3 glow lamp manufactured by General Electricand operating in the approximate range of 2800 to 2900 Angstrom units.

Since the first detector element is fabricated from a metal which isrendered electronegative by the action of the ultraviolet ray radiation,the grid 72 of the thyratron tube 62 and the first detector element 36are floating from a potential standpoint.

The second detector element 38 is connected through a resistance 74 tothe pulsating DC. voltage from the rectifier 58 and is thus maintainedat the same potential as the anode 60 of the thyratron tube 62. Thethird detector element 40 is connected through a resistance 76 to thelead 54 and is thus supplied with AC. potential.

A relay 80 is connected to the output of the thyratron tube 62 and whenenergized by the thyratron tube 62 causes simultaneous energization of aholding relay 82 whose output 84 is connected to a suitable alarm orother device intended to give notice of the existence of smokeconditions and the possible existence of a confiagration constitutingthe source of the same.

The maintenance of the grid 72 of the thyratron tube at floatingpotential to maintain the thyratron tube 62 at cut-off depends onseveral factors, among them being the distance between the ultravioletradiation source 26 and the total energy of its saturation constant; thedistance between the first and second detector elements 36 and 38; theresistance in ohms of the resistor 70; the capacitance on the capacitor64 and the condition of the air between the detector elements 36, 38,and 40.

When the proper relationship between these elements is accomplished bythe methods well-known to those skilled in the art, the grid 72 will bemaintained in floating bias and the thyratron tube 62 maintained atcutoff to prevent energization of the relays 80 and 82 and the alarm 84associated therewith.

However, should smoke infiltrate into the field of the detector elements36, 38, and 40, the smoke particles will be acted upon by the electronsand positive ions between the detector elements to accomplish ionizationof the same. The positive ions are attracted to the previouslyelectronegative first detector element 36 and the electrons areattracted to the second detector element 38. The positive ions attractedto the first detector element 36 alter the electronegativecharacteristic of said first detector element and raise the potential ofthe grid 72 of the thyratron tube 62 sufiiciently to cause the thyratrontube 62 to fire so that the relays and 82 are simultaneously energizedto introduce a signal to the output 84 of the relay 82.

The thyratron 62, when energized, discharges the capacitor 64 and thethyratron 62 is thus returned to cutolf and will remain at the cut-offuntil smoke once again enters the field of the first, second, and thirddetector elements 36, 38, and 40. The capacitor 66 acts as a limitingcapacitor to prevent recurrent energization of the thyratron 62 once therelay 84 has been energized in the above described manner.

The manner in which the electronegative plate 36 functions when exposedto ultraviolet radiation is graphically illustrated in Fig. 5 of thedrawings. When exposed to ultraviolet radiation, the plate 36 becomeselectronegative and the positive ions are attracted to the plate 38.When smoke enters the field between the plates 36 and 38, the plate 36becomes less electronegative and the grid 72 of the thyratron 62discharges said thyratron to discharge the capacitor 64.

We thus provide by our invention a smoke detector which is characterizedby its extreme sensitivity attributable, in large part, to theutilization of detecting elements having different levels of sensitivityto an ultraviolet radiation source rendering at least one of theelements more electronegative than an associated element, theelectronegative element being associated with the grid of a thyratrontube to control the energization of the same and the energization of awarning signal circuit.

We claim:

1. In a smoke detecting device, the combination of: a source ofultraviolet rays; a first detector element exposed to said source andsensitive thereto; a second detector element exposed to said source andinsensitive thereto; a normally inoperative circuit connecting saidfirst and second detector elements in operative relationship with eachother; and signal emitting means operable by said circuit upon theexposure of said detector elements to smoke.

2. In a smoke detecting device, the combination of: a source ofultraviolet rays; a first detector element exposed to said source andsensitive thereto, said first detector element incorporating selenium asthe ultraviolet ray sensitive medium; a second detector element exposedto said source and insensitive thereto, said second detector elementincorporating carbon as the ultraviolet ray insensitive medium; anormally inoperative circuit connecting said first and second detectorelements in operative relationship with each other; and signal emittingmeans operable by said circuit upon the exposure of said detectorelements to smoke.

3. In a smoke detecting device, the combination of: a source ofultraviolet rays; a first detector element exposed to said source andsensitive thereto, said first de tector element incorporating zinc asthe ultraviolet ray sensitive medium; a second detector element exposedto said source and insensitive thereto, said second detector elementincorporating copper as the ultraviolet ray insensitive medium; anormally inoperative circuit connecting said first and second detectorelements in operative relationship with each other; and signal emittingmeans operable by said circuit upon the exposure of said detectorelements to smoke.

4. In a smoke detecting device, the combination of: a source ofultraviolet radiation; a first ultraviolet ray sensitive detectorexposed to said radiation; 21 second ultraviolet ray insensitivedetector juxtaposed to said first detector; a normally inoperativecircuit operatively connecting said first and second detectors; andsignal emitting means connected in said circuit and energizable therebywhen smoke in the field between said detectors causes the energizationof said circuit.

5. In a smoke detecting device, the combination of: a source ofultraviolet radiation; first and second detectors having differentlevels of sensitivity to said radiation; a normally inoperative circuitconnecting said first and second detectors in operative relationshipwith each other; and signal emitting means operatively connected in saidcircuit and energizable thereby when smoke in the field between saiddetectors causes the energization of said circuit.

6. In a smoke detector, the combination of: a source of ultravioletradiation; first and second detectors juxtaposed to said source, one ofsaid detectors being normally rendered electronegative by saidradiation; a circuit incorporating said detectors and being maintainedinoperative by said electronegative detector; and a signal operativelyconnected in said circuit and energizable thereby when saidelectronegative detector is rendered less negative by the passage ofsmoke into the field of said detectors to cause the energization of saidcircuit.

7. In a smoke detector, the combination of: a source of ultravioletradiation; first and second detectors juxtaposed to said source, one ofsaid detectors being normally rendered electronegative by said radiationand said detectors being constituted by spaced plates contiguous to saidsource; a circuit incorporating said detectors and being maintainedinoperative by said electronegative detector; and a signal operativelyconnected in said circuit and energizable thereby when saidelectronegative deinto the field of said detectors to cause theenergization of said circuit. I

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